Why moa? part 2: frogs, like mammals, have failed to undergo evolutionary radiation in New Zealand

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...continued from https://www.inaturalist.org/journal/milewski/60765-why-moa-part-1#

Please see

https://www.youtube.com/watch?v=l30DyDLK1pw

https://explorebioedge.com/2015/03/15/the-riddle-of-the-failed-frogs-of-gondwana/

https://www.inaturalist.org/journal/milewski/68213-comments-on-the-frog-anuran-fauna-of-tasmania-w-r-t-evolutionary-convergence

Posted on September 3, 2024 10:20 PM by

milewski

Comments

It's quite a thought-provoking video. Although you seem to have taken it down so I can't really comment on it to a great extent (i'm trying to remember the points). I would probably suggest that our frog fauna was pretty standard for an island that is situated in the climatic zone that it is. We had six species of endemic frogs when the first humans arrived in Aotearoa/New Zealand (potentially more given the poor fossil record over here), and these ranged from the relatively large Waitomo frog (100mm SVL) to what we have left today. I believe this species was even theorised to be highly aquatic based on its morphology. When we compare this to another island group in a similar climate - the British Isles - we find that they also have relatively poor diversity in their frogs and toads (4 species). The Seychelles, although small, are situated roughly within the tropics and are probably geared towards having a higher diversity given the nature of this region. Patagonia on the other hand although likely to have been greatly impacted by glaciation, as New Zealand was, was probably less impacted by the Oligocene drowning due to its geography. There is also the fact that it is part of a continental landmass, which also has extremely high endimism in amphibians (more than 2,500 species), and would allow for recolonisation from the north if the region became unsuitable for amphibians during certain timespans.

I think it is very likely that there are ecological, and climatic factors at play for why primitive terrestrial mammals didn't survive and diversify in NZ. These will have most certainly played a role in the historical extinctions of our crocodilians and turtles, and I don't see why it couldn't also hold true for our mammals. I believe they were quite basal (close to monotremes), and so it's impossible to say that their physiology or ecology was suitable for a cooling climate. Undoubtedly the Quaternary glaciation events have played a role in the current diversity of our fauna and flora.

Posted by timharker 13 days ago

@timharker

Many thanks for your thoughtful comments, from which I learned a lot.

Posted by milewski 12 days ago

Why moa? part 2: frogs, like mammals, have failed to undergo evolutionary radiation in New Zealand

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